Resources

Emission Inventory Background Information

The page last reviewed April 25, 2011

About Emissions Data

The California Air Resources
Board (ARB) has collected information on emissions from air
pollution sources since 1969. This information is
periodically compiled by State and local air pollution
control agencies to create an emission inventory --- an important
building block in the development of the State's
air pollution control program.

The staff at the ARB compiles
data to create the criteria pollutant emission inventory which
includes information on the emissions of reactive organic gases (ROG),
oxides of nitrogen (NOx), oxides of sulfur
(SOx), carbon monoxide (CO), and particulate matter (PM10).
Data are gathered on an ongoing basis and stored
in the California Emission Inventory Development and Reporting System
(CEIDARS). A summary of the criteria pollutant
inventory is published annually. The California emission
inventory contains information on the following air
pollution sources:

Stationary sources
- approximately
13,000 individual facilities, called point sources. Point
sources are fixed pollution sources such as electric power plants and
refineries. There are also about 135 aggregated point source
categories. These categories estimate emissions for the
non-point source stationary sources;

Area-wide sources - approximately 80 source categories.
An area-wide source category is made up of sources of
pollution mainly linked to the activity of people. Examples
of these sources include consumer products and architectural coatings
used in a region; and

Mobile sources - all on-road vehicles such as automobiles and
trucks; off-road vehicles such as trains, ships, aircraft; and farm
equipment.

The principal agencies
contributing data to the stationary and area-wide source inventory
are the ARB and the California air pollution control and air quality
management districts. The ARB, the California
Department of Transportation (CALTRANS), and regional transportation
agencies are the principal agencies involved
in developing the mobile source inventory.

The information represented in
the California emission inventory is a snap-shot of a variety
of dynamic and variable processes. As such, the emission
inventory can only represent an estimate of what
is actually occurring. Due to the importance of the inventory
in air quality planning and management, the
ARB and local air pollution control agencies are working together to
further refine estimation methods to improve
the inventory.

Toxics Emission
Inventory Data

The ARB also collects toxic
emissions from thousands of facilities in California. The
toxic pollutant inventory is updated every four years and is stored in
CEIDARS. For more information concerning
the toxic program, see the Air Toxics "Hot Spots"
Program.

The Air Resources Board,
Emission Inventory Branch is the keeper of all California emissions
data. Members of the public, regulatory agencies, industry groups, and
environmental groups can search for criteria
and toxics emissions information on particular facilities using the
Facility Search Engine.
For more information, please
contact the
Emission Inventory Branch at (916) 322-5350.